Audio speaker with back volume containing adsorptive material

ABSTRACT

An audio speaker having a speaker housing surrounding a back volume that is divided into a rear cavity behind a speaker driver and an adsorption cavity separated from the rear cavity by a permeable partition, is disclosed. More particularly, the adsorption cavity may be defined between the speaker housing and the permeable partition, and may be directly filled with adsorptive particles to adsorb gas during sound generation. The permeable partition may allow the gas to flow between the rear cavity and the adsorption cavity, and may retain the adsorptive particles within the adsorption cavity. Other embodiments are also described and claimed.

BACKGROUND

Field

Embodiments related to an audio speaker having a speaker housingsurrounding a back volume that is divided into several cavities by apermeable partition, are disclosed. More particularly, an embodimentrelated to a multi-cavity back volume within a speaker housing, themulti-cavity back volume having a cavity defined between the speakerhousing and a permeable partition, and that may be filled with anadsorptive material to adsorb gas during sound generation, is disclosed.

Background Information

A portable consumer electronics device, such as a mobile phone, a tabletcomputer, or a portable media device, typically includes a systemenclosure surrounding internal system components, such as audiospeakers. Such devices may have small form factors with limited internalspace, and thus, the integrated audio speakers may be micro speakers,also known as microdrivers, that are miniaturized implementations ofloudspeakers having a broad frequency range. Due to their small size,micro speakers tend to have limited space available for a back volume.Furthermore, given that acoustic performance in the low frequency audiorange usually correlates directly with the back volume size, microspeakers tend to have limited performance in the bass range. However,the low frequency acoustic performance of portable consumer electronicsdevices having micro speakers may be increased by increasing the backvolume size as much as possible within the internal space available inthe system enclosure.

SUMMARY

Portable consumer electronics devices, such as mobile phones, havecontinued to become more and more compact. As the form factor of suchdevices shrinks, system enclosures become smaller and the spaceavailable for speaker integration is reduced. More particularly, thespace available for a speaker back volume decreases, and along with it,low frequency acoustic performance diminishes. However, as describedbelow, the effective back volume of a portable consumer electronicsdevice may be increased without increasing the actual physical size ofthe back volume. More particularly, an adsorbent material may beincorporated within the back volume to lower the frequency of thenatural resonance peak and thereby make bass sounds louder. Theadsorbent material may reduce the spring rate of the speaker byadsorbing and desorbing air molecules as pressure fluctuates within theback volume during sound generation. Such adsorption/desorption mayincrease system efficiency at lower frequencies to produce more audiopower. Thus, the audio speaker may produce better sound in the same formfactor, or produce equivalent sound in a smaller form factor. However,directly incorporating an adsorbent material within the back volume toimprove acoustic performance may cause side effects. In particular,incorporating loose adsorbent particles directly within the back volumemay create a system that is physically unbalanced and susceptible todamage as the particles shift, e.g., due to the mobile device beingcarried or moved by a user. Furthermore, attempting to mitigate theseeffects by packaging the adsorbent particles in a secondary enclosure,e.g., a mesh bag, that is then located in the back volume may costprecious enclosure space, as the secondary enclosure walls occupyvertical clearance in the back volume. Thus, for adsorbent materials tobe used in a speaker back volume to enhance acoustic performance withinthe smallest possible form factor, an audio speaker having a speakerenclosure that physically isolates an adsorbent material from sensitivedriver components without adding additional system thickness may beneeded.

In an embodiment, an audio speaker includes a housing defining a backvolume behind a speaker driver. The back volume may be divided intoseveral cavities by a permeable partition that is coupled with thehousing along a perimeter of the partition. More particularly, thepermeable partition may divide the back volume into a rear cavity and anadsorption cavity. The rear cavity may be defined between, or enclosedby, the speaker driver, the housing, and a first side of the permeablepartition. Similarly, the adsorption cavity may be defined between thehousing and a second side of the permeable partition. An adsorptivefiller that is to adsorb a gas may be directly loaded into theadsorption cavity. That is, the adsorptive filler directly contacts theinside of a wall of the housing and the adsorption cavity side of thepermeable partition. Furthermore, the permeable partition may includeone or more holes between the first side and the second side (extendingthrough the partition from the adsorption cavity side to the other side)to place the rear cavity in fluid (gaseous) communication with theadsorption cavity, while at the same time preventing the adsorptivefiller from passing from the adsorption cavity into the rear cavity. Forexample, each of the holes in the permeable partition may havedimensions smaller than a size of the adsorptive filler such that theadsorptive filler is retained within the adsorption cavity by thepermeable partition. In an embodiment, retention of the adsorptivefiller within the adsorption cavity may be further enhanced by providinga seal, e.g., a hermetic seal, between the permeable partition and thehousing.

The rear cavity and the adsorption cavity of the back volume may beadjacent to each other, but may have a relative orientation that differsin various embodiments. For example, the speaker driver may include adiaphragm that moves along a central axis, and the rear cavity may bedirectly behind the diaphragm along the central axis. However, theadsorption cavity may be laterally offset from the rear cavity away fromthe central axis. That is, a normal vector emerging from the first sideof the permeable partition and pointing into the rear cavity is orientedin a direction that is orthogonal to the central axis, e.g., the rearcavity and the adsorption cavity may each be flat and thin andpositioned side-by-side. Alternatively, the adsorption cavity may bedirectly behind the rear cavity along the central axis such that thenormal vector from the first side of the permeable partition points intothe rear cavity in a direction parallel to the central axis.

In an embodiment, the adsorptive filler may partially, substantially, orcompletely fill the adsorption cavity. For example, the adsorptivefiller may cover a portion of the housing within the adsorption cavity,e.g., may coat an inner surface of the housing. The adsorptive fillermay include unbound particles, such as a granular composition of one ormore of a zeolite material and/or an activated carbon material. Thegranular materials may be inserted into the adsorption cavity through afill port extending through the housing wall between the adsorptioncavity and a surrounding environment outside of the housing, and a plugmay be located in the fill port to seal the adsorption cavity andprevent the adsorptive filler from passing through the fill port intothe surrounding environment (and the plug may also perform as a hermeticseal to prevent gaseous flow out through the fill port).

A method of forming an audio speaker with a multi-cavity back volumeincludes overmolding the housing around the permeable partition. Moreparticularly, the method may include molding the housing around theperimeter of the permeable partition such that the back volume iscreated with the rear cavity and the adsorption cavity placed in fluidcommunication through the holes in the permeable partition. The speakerdriver may be mounted in a driver port, which may be integrally formedwith the housing, such that the rear cavity is defined between thespeaker driver, the housing, and the first side of the permeablepartition. Furthermore, a fill port may be integrally formed with thehousing to allow the adsorptive filler to be poured, injected, sprayed,or otherwise inserted into the adsorption cavity through the fill port.After filling the adsorption cavity with the adsorptive filler, the fillport may be sealed by a plug such that the adsorption cavity is definedbetween the plug, the housing, and the second side of the permeablepartition. Accordingly, the audio speaker may be built with a directlyfilled adsorption cavity separated from a rear cavity by an acousticallytransparent barrier that allows sound to drive the adsorption anddesorption of air molecules within an adsorptive filler and therebyincrease the overall output power of the audio speaker, especially inthe low frequency audio range.

The above summary does not include an exhaustive list of all aspects ofthe present invention. It is contemplated that the invention includesall systems and methods that can be practiced from all suitablecombinations of the various aspects summarized above, as well as thosedisclosed in the Detailed Description below and particularly pointed outin the claims filed with the application. Such combinations haveparticular advantages not specifically recited in the above summary.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial view of an electronic device in accordance with anembodiment.

FIG. 2 is a sectional view of an audio speaker of an electronic devicein accordance with an embodiment.

FIGS. 3A-3B are cross-sectional views, taken about line A-A of FIG. 2,of a permeable partition of an audio speaker in accordance with anembodiment.

FIG. 4 is a cross-sectional view, taken about line B-B of FIG. 3A, of asealed portion of an audio speaker in accordance with an embodiment.

FIGS. 5A-5B are cross-sectional views, taken about line C-C of FIG. 2,of an adsorption cavity of an audio speaker in accordance with anembodiment.

FIGS. 6A-6B are cross-sectional views, taken about line D-D of FIG. 2,of a plugged portion of an audio speaker in accordance with anembodiment.

FIG. 7 is a sectional view of an audio speaker of an electronic devicein accordance with an embodiment.

FIG. 8 is a flowchart of a method of forming an audio speaker having amulti-cavity back volume in accordance with an embodiment.

FIG. 9 is a schematic view of an electronic device having a microspeaker in accordance with an embodiment.

DETAILED DESCRIPTION

Embodiments describe an audio speaker having a speaker housingsurrounding a back volume that is divided into several cavities (one ofwhich contains an adsorbent material) by a permeable partition. However,while some embodiments are described with specific regard to integrationwithin mobile electronics devices, such as handheld devices, theembodiments are not so limited and certain embodiments may also beapplicable to other uses. For example, an audio speaker as describedbelow may be incorporated into other devices and apparatuses, includingdesktop computers, laptop computers, or motor vehicles, to name only afew possible applications.

In various embodiments, description is made with reference to thefigures. However, certain embodiments may be practiced without one ormore of these specific details, or in combination with other knownmethods and configurations. In the following description, numerousspecific details are set forth, such as specific configurations,dimensions, and processes, in order to provide a thorough understandingof the embodiments. In other instances, well-known processes andmanufacturing techniques have not been described in particular detail inorder to not unnecessarily obscure the description. Reference throughoutthis specification to “one embodiment,” “an embodiment,” or the like,means that a particular feature, structure, configuration, orcharacteristic described is included in at least one embodiment. Thus,the appearance of the phrase “one embodiment,” “an embodiment,” or thelike, in various places throughout this specification are notnecessarily referring to the same embodiment. Furthermore, theparticular features, structures, configurations, or characteristics maybe combined in any suitable manner in one or more embodiments.

The use of relative terms throughout the description may denote arelative position or direction. For example, “forward” may indicate afirst direction away from a reference point. Similarly, “behind” or“rear” may indicate a location in a second direction from the referencepoint opposite from the first direction. However, such terms are notintended to limit the use of an audio speaker to a specificconfiguration described in the various embodiments below. For example, amicro speaker may be oriented to radiate sound in any direction withrespect to an external environment, including upward toward the sky anddownward toward the ground.

In an aspect, an audio speaker may include a speaker housing thatincorporates a multi-cavity back volume in a space efficient manner. Thehousing may at least partially define each cavity in the back volume,and the cavities may be in fluid communication with each other, i.e.,air and sound may flow between the cavities. For example, a permeablepartition may extend directly across the back volume such that thecavities are defined by the housing and the partition wall. Thepermeable partition may be supported by the housing, and in anembodiment, the permeable partition is sealed to the housing by ahermetic seal. At least one of the cavities, i.e., an “adsorptioncavity,” may contain an adsorbent material, such as a volume of unboundadsorbent particles, which adsorb and desorb air as pressure fluctuatesin the adsorption cavity due to sound traveling between the cavitiesduring sound generation. Thus, a multi-cavity back volume may be formedin a space efficient manner since the housing may form part of theenclosure that constrains the adsorption material, thereby eliminating aneed for a secondary enclosure, e.g., a mesh bag, to constrain theadsorptive particles within the adsorption cavity.

In an aspect, an audio speaker may have a permeable partition separatingan adsorption cavity, in which adsorptive filler is located, from a rearcavity, in which audio speaker components are located. The permeablepartition may include holes that are large enough to permit air to flowin and out of the adsorption cavity. Thus, the permeable partition maybe acoustically transparent. However, the holes may be small enough toprevent an adsorptive material from sifting outward into the rearcavity. Accordingly, the permeable partition separating the cavities mayallow the adsorptive material to adsorb and desorb air molecules inresponse to pressure variations to lower the natural resonance peak ofthe audio speaker while reducing the likelihood that the adsorptivematerial will intrude into and damage sensitive speaker components, suchas a voicecoil or a diaphragm housed in the rear cavity.

Referring to FIG. 1, a pictorial view of an electronic device is shownin accordance with an embodiment. Electronic device 100 may be asmartphone device. Alternatively, it could be any other portable orstationary device or apparatus, such as a laptop computer or a tabletcomputer. Electronic device 100 may include various capabilities toallow the user to access features involving, for example, calls,voicemail, music, e-mail, internet browsing, scheduling, and photos.Electronic device 100 may also include hardware to facilitate suchcapabilities. For example, an integrated microphone 102 may pick up thevoice of a user during a call, and an audio speaker 106, e.g., a microspeaker, may deliver a far-end voice to the near-end user during thecall. Audio speaker 106 may also emit sounds associated with music filesplayed by a music player application running on electronic device 100. Adisplay 104 may present the user with a graphical user interface toallow the user to interact with electronic device 100 and/orapplications running on electronic device 100. Other conventionalfeatures are not shown but may of course be included in electronicdevice 100.

Referring to FIG. 2, a sectional view of an audio speaker of anelectronic device is shown in accordance with an embodiment. In anembodiment, an audio speaker 106 includes an enclosure, such as aspeaker housing 204, which supports a speaker driver 202. Speaker driver202 may be a loudspeaker used to convert an electrical audio signal intoa sound. For example, speaker driver 202 may be a micro speaker having adiaphragm 206 supported relative to housing 204 by a speaker surround208. Speaker surround 208 may flex to permit axial motion of diaphragm206 along a central axis 210. For example, speaker driver 202 may have amotor assembly attached to diaphragm 206 to move diaphragm 206 axiallywith pistonic motion, i.e., forward and backward, along central axis210. The motor assembly may include a voicecoil 212 that moves relativeto a magnetic assembly 214. In an embodiment, magnetic assembly 214includes a magnet, such as a permanent magnet, attached to a top plateat a front face and to a yoke at a back face. The top plate and yoke maybe formed from magnetic materials to create a magnetic circuit having amagnetic gap within which voicecoil 212 oscillates forward and backward.Thus, when the electrical audio signal is input to voicecoil 212, amechanical force may be generated that moves diaphragm 206 to radiatesound forward along central axis 210 into a surrounding environmentoutside of housing 204.

Movement of diaphragm 206 to radiate sound forward toward thesurrounding environment may cause sound to be pushed in a rearwarddirection. For example, sound may propagate through a gas filling aspace enclosed by housing 204. More particularly, sound may travelthrough air in a back volume 216 behind diaphragm 206. Back volume 216may influence acoustic performance. In particular, the size of backvolume 216 may influence the natural resonance peak of audio speaker106. For example, increasing the size of back volume 216 may result inthe generation of louder bass sounds.

In an embodiment, back volume 216 within housing 204 may be separatedinto several cavities. For example, back volume 216 may be separatedinto a rear cavity 218 and an adsorption cavity 220 by a permeablepartition 222. Rear cavity 218 may be located directly behind speakerdriver 202. That is, speaker driver 202 may be suspended or supportedwithin rear cavity 218 such that sound radiating backward from diaphragm206 propagates directly into rear cavity 218. Accordingly, at least aportion of rear cavity 218 may be defined by a rear surface of diaphragm206, and similarly, by a rear surface of speaker surround 208.Furthermore, given that permeable partition 222 may extend across across-sectional area of back volume 216 between several walls of housing204, rear cavity 218 may be further defined by an internal surface ofhousing 204 and a first side 224 of permeable partition 222.

Back volume 216 may include adsorption cavity 220 separated from rearcavity 218 by permeable partition 222. That is, adsorption cavity 220may be adjacent to rear cavity 218 on an opposite side of permeablepartition 222. In an embodiment, adsorption cavity 220 is defined by aninternal surface of housing 204 that surrounds back volume 216, and mayalso be defined by a second side 226 of permeable partition 222. Thus,rear cavity 218 and adsorption cavity 220 may be immediately adjacent toone another across permeable partition 222.

In an embodiment, adsorption cavity 220 may be placed in fluidcommunication with the surrounding environment through a fill port 228.For example, fill port 228 may be a hole through a wall of housing 204that places adsorption cavity 220 in fluid communication with thesurrounding environment. The port may be formed during molding ofhousing 204, or through a secondary operation, as described furtherbelow. To isolate adsorption cavity 220 from the surroundingenvironment, a plug 230 may be located in fill port 228, e.g., afterfilling adsorption cavity 220 with an adsorptive filler 232, to preventleakage of the adsorptive filler 232 into the surrounding environment.Thus, adsorption cavity 220 may be partially defined by a surface ofplug 230.

Audio speaker 106 may have a form factor with any number of shapes andsizes. For example, audio speaker 106, and thus housing 204, may have anexternal contour that appears to be a combination of hexahedrons,cylinders, etc. One such external contour could be a thin box, forexample. Furthermore, housing 204 may be thin-walled, and thus, across-sectional area of a plane passing across housing 204 at any pointmay have a geometry corresponding to the external contour, includingrectangular, circular, and triangular, etc. Accordingly, permeablepartition 222 extending across back volume 216 within housing 204 mayalso have a variety of profile shapes. For example, in the case whereaudio speaker 106 is a hexahedron, e.g., a low-profile box having arectangular profile extruded in a direction orthogonal to central axis210, permeable partition 222 may have a rectangular profile.

Adsorptive filler 232 may be packaged in adsorption cavity 220 bydirectly filling, e.g., packing, adsorption cavity 220 with a looseadsorptive material and/or by coating inner surfaces of housing 204 withan adsorptive material. Directly filling adsorption cavity 220 may bedistinguished from indirectly filling adsorption cavity 220 in that theloose adsorptive material may be poured, injected, or other transferredinto adsorption cavity 220 in a loose and unconstrained manner such thatthe adsorptive material may move freely within adsorption cavity 220.That is, the adsorptive material may be constrained only by the wallsthat define adsorption cavity 220, e.g., an inner surface of housing204, and not by a separate constraint, e.g., a bag, pouch, box, etc.that is filled with adsorptive material prior to or after inserting theseparate constraint into adsorption cavity 220. Potential processes forfilling adsorption cavity 220 with adsorptive material are describedfurther below, but in an embodiment, at least a portion of the space ofadsorption cavity 220 is filled with adsorptive filler 232, and at leasta portion of an inner surface of housing 204 within adsorption cavity220 is covered by adsorptive filler 232. The adsorptive filler 232 maybe any appropriate adsorptive material that is capable of adsorbing agas located in back volume 216. For example, adsorptive filler 232 mayinclude an adsorptive material such as a zeolite, activated carbon,silica, alumina, etc., which are configured to adsorb air molecules. Theadsorptive material may be in a loose granular form. More particularly,the adsorptive filler 232 may include unbound particles that are able tomove freely within adsorption cavity 220, e.g., the particles may shakearound during device use. Thus, permeable partition 222 may act as abarrier to prevent adsorptive filler 232 from shaking out of adsorptioncavity 220 into rear cavity 218 behind speaker driver 202.

Referring to FIG. 3A, a cross-sectional view, taken about line A-A ofFIG. 2, of a permeable partition of an audio speaker is shown inaccordance with an embodiment. In an embodiment, permeable partition 222may include a film or a sheet extending across back volume 216 betweenopposing walls of an inner surface 302 of housing 204. For example,permeable partition 222 may be a thin plastic or metallic plate. Athickness of permeable partition 222 may be on the order of 0.1 to 5millimeter. A perimeter 304 of permeable partition 222 may be, forexample, an outer edge of first side 224 or second side 226 of permeablepartition 222. Alternatively, perimeter 304 may be an outer wallextending between the sides of permeable partition 222, i.e., may be anouter rim of permeable partition 222. In any case, perimeter 304 may becoincident with inner surface 302 such that permeable partition 222 issealed against housing 204 to prevent a gas, e.g., air, and/oradsorptive filler 232, from leaking around permeable partition 222between adsorption cavity 220 and rear cavity 218. Inner surface 302 mayprovide an inner dimension of a housing wall of housing 204. Moreparticularly, housing 204 may include a housing wall with a thicknessextending from inner surface 302 adjacent to perimeter 304 of permeablepartition 222 and an outer surface that provides an outer dimension ofthe housing wall. Thus, housing 204 may have a housing wall that forms acase or enclosure around permeable partition 222.

In an embodiment, permeable partition 222 is to allow a gas, e.g., air,to flow freely between rear cavity 218 and adsorption cavity 220 of backvolume 216 through partition thickness. Permeable partition 222 mayinclude one or more holes 306 that are larger than the constituentmolecules of air, and thus allows air to flow from first side 224 tosecond side 226 of permeable partition 222. Thus, permeable partition222 may be acoustically transparent, since air molecules may freelytransmit pressure changes caused by sound generation. Several holes 306of the same or different cross-section dimensions may be formed throughpermeable partition 222. For example, permeable partition 222 mayinclude a first set of several circular holes 306 with diameters on theorder of 5 nanometer to 100 micrometer, and a second set of holes orslots, e.g., transverse slits 308, having widths on the order of 5nanometer to 100 micrometer and lengths on the order of 5 nanometer to500 micrometer. These hole shapes and dimensions are provided by way ofexample only, and may be varied within the scope of this description toprovide passages through which air may pass from rear cavity 218 toadsorption cavity 220 to create an acoustically transparent permeablepartition 222.

Referring to FIG. 3B, a cross-sectional view, taken about line A-A ofFIG. 2, of a permeable partition of an audio speaker is shown inaccordance with an embodiment. In an embodiment, permeable partition 222includes a mesh structure extending across back volume 216 fromperimeter 304 at inner surface 302 of housing 204. The mesh structuremay include several strands 310 of flexible material, e.g., plastic ormetal strands 310, which are woven, knitted, etc., to form a web-likestructure with holes 306 between strands 310. As an example, permeablepartition 222 may be a polyester mesh. Other processes, such asexpanding plastic sheeting to produce a porous sheet, may also be usedto form permeable partition 222 with acoustically transparent passages.The pitch and spacing between strands 310 may be selected and formed tocreate holes 306 having dimensions that allow air to flow acrosspermeable partition 222 between rear cavity 218 and adsorption cavity220. The dimension of strands 310 may be selected accordingly. Forexample, mesh strands 310 may have a diameter on the order of 0.1 to 5mm.

In an embodiment, the holes 306 in permeable partition 222 are sized toprevent adsorptive filler 232 from escaping adsorption cavity 220through the partition. For example, holes 306 and/or slits 308 ofpermeable partition 222 may include dimensions that are smaller than amaximum dimension of adsorptive filler 232 particles. In an embodiment,adsorptive filler 232 includes particles having outer dimensions on theorder of 10 nanometer to 500 micrometer. Thus, depending on the sizerange of adsorptive filler 232 particles that are used to filladsorption cavity 220, permeable partition 222 may include holes 306 onthe order of 9 nanometer to 499 nanometer. In an example, if the outerdimension of adsorptive filler 232 particles in adsorption cavity 220range between 50 to 150 micrometer, then holes 306 and/or slits 308 mayhave a maximum dimension of less than 50 micrometer, e.g., 40micrometer, to retain even the smallest particles in adsorption cavity220.

Referring to FIG. 4, a cross-sectional view, taken about line B-B ofFIG. 3A, of a sealed portion of an audio speaker is shown in accordancewith an embodiment. Permeable partition 222 may be sealed alongperimeter 304 to prevent escape of adsorptive filler 232 around an outeredge of permeable partition 222 into rear cavity 218. More particularly,partition wall 402 may engage a slot formed in an inner surface 302 ofhousing 204 such that the surface of the slot overlaps a portion offirst side 224 or second side 226. The overlap of permeable partition222 and housing 204 may be sufficient to prevent adsorptive filler 232from escaping adsorption cavity 220. For example, the slot in housing204 and overlap between permeable partition 222 and housing 204 may beformed by overmolding housing 204 around permeable partition 222. Insuch case, permeable partition 222 may be joined to housing 204 alongthe overmolded surfaces such that a seal is formed to resist movement ofadsorptive filler 232 around permeable partition 222. The joint may havegaps that range in dimension from zero to the smallest particledimension of adsorptive filler 232. When the gap is essentially zero,the joint may form a hermetic seal.

Optionally, the barrier between adsorption cavity 220 and rear cavity218, and more particularly the joint between perimeter 304 and housing204, may be enhanced by forming a seal 404 at the interface betweenhousing 204 and permeable partition 222. For example, a bead of adhesiveor epoxy, e.g., silicone, may be applied at the interface to form ahermetic seal that prevents the migration of both adsorptive filler 232and air around the outer edge of permeable partition 222. Thus, seal 404may be applied on one or both of first side 224 or second side 226 ofpermeable partition 222 to form an airtight seal between permeablepartition 222 and housing 204.

A hermetic seal may be formed with or without a separate seal 404 at theinterface between housing 204 and permeable partition 222. That is, whenthe gap between housing 204 and permeable partition 222 is essentiallyzero, the joint may form a hermetic seal that ensures that sound airflow(due to the speaker driver in operation) does not pass around perimeter304 of partition wall 402, and is instead confined to the predeterminedholes 306 in partition wall 402. However, the addition of separate seal404, e.g., a bead of sealant, may assist in forming the hermetic seal,and furthermore, may provide a mechanical bond between housing 204 andpartition wall 402 to secure the components relative to each other.

Referring to FIG. 5A, a cross-sectional view, taken about line C-C ofFIG. 2, of an adsorption cavity of an audio speaker is shown inaccordance with an embodiment. As described above, adsorption cavity 220may include adsorptive filler 232, which may include any combination ofadsorptive materials, including activated carbon and zeolite materials.Adsorptive filler 232 may be in a particulate form, e.g., granularpowder, and thus may move freely within adsorption cavity 220 anddirectly contact surfaces of permeable partition 222 and housing 204. Asshown in FIG. 5A, adsorptive filler 232 may partially fill adsorptioncavity 220, i.e., the total volume of adsorptive filler 232 may be lessthan the volume of adsorption cavity 220. This may be the case, forexample, when a layer of adsorptive filler 232 is coated over innersurface 302 using known coating techniques.

In an embodiment, adsorptive filler 232 may cover at least a portion ofinner surface 302. For example, gravity may cause adsorptive filler 232particles to settle to a bottom side of adsorption cavity 220 and theparticles may cover the bottom inner surface 302 of housing 204 withinadsorption cavity 220. In an alternative embodiment, at least a portionof the adsorptive filler 232 particles may adhere to inner surface 302through native surface adhesion, or through the addition of an adhesivetherebetween. For example, adsorptive filler 232 particles may be coatedover an adhesive layer on inner surface 302 such that the particlesadhere around a periphery of adsorption cavity 220, as shown in FIG. 5A.That is, particles may at least partially cover several internal wallsof adsorption cavity 220. Thus, adsorptive filler 232 may cover innersurface 302 around adsorption cavity 220.

Referring to FIG. 5B, a cross-sectional view, taken about line C-C ofFIG. 2, of an adsorption cavity of an audio speaker is shown inaccordance with an embodiment. In an embodiment, adsorptive filler 232substantially or completely fills adsorption cavity 220. For example,adsorptive filler 232 may be packed into adsorption cavity 220 such thatat least 50% of the volume of adsorption cavity 220 is filled by thepacked particulate volume. This packing volume may include the spacesbetween the particles. For example, a volume of the particulate matterand a volume of the interstitial spaces between particles may be atleast 75% of the volume of adsorption cavity 220, and in some cases atleast 90% of the volume of adsorption cavity 220. In an embodiment, noneof the volume of adsorptive cavity 220 is occupied by secondarycontainers, such as mesh bag walls or films, surrounding adsorptivefiller 232.

Referring to FIG. 6A, a cross-sectional view, taken about line D-D ofFIG. 2, of a plugged portion of an audio speaker is shown in accordancewith an embodiment. In an embodiment, housing 204 includes plug 230disposed within fill port 228 to prevent adsorptive filler 232 fromleaking out of adsorption cavity 220. For example, plug 230 may beshaped to engage fill port 228 such that a surface of plug 230 forms apress fit against a surface of fill port 228 to create a stopper thatseals adsorption cavity 220. Plug 230 may also be welded, e.g.,chemically or thermally, to housing 204 within fill port 228 to form apermanently sealed plug.

Referring to FIG. 6B, a cross-sectional view, taken about line D-D ofFIG. 2, of a plugged portion of an audio speaker is shown in accordancewith an embodiment. In an embodiment, plug 230 may have a grommet shapewith a central body and upper and lower collars that seal against aninner surface 302 and an outer surface of housing 204. The central bodymay seal against housing 204 within fill port 228. The grommet plug maybe formed prior to insertion within fill port 228. Alternatively, plug230 may be formed from an adhesive, e.g., a temperature or light-curedadhesive, an epoxy, or a molten plastic or metal that is flowed intofill port 228 and thereafter cured or cooled such that plug 230 hardensin place to create a permanently sealed plug 230 to seal adsorptioncavity 220.

Referring to FIG. 7, a sectional view of an audio speaker of anelectronic device is shown in accordance with an embodiment. Rear cavity218 and adsorption cavity 220 may have different relative orientationsin various embodiments. For example, as shown in FIG. 2, in anembodiment, adsorption cavity 220 is located lateral to rear cavity 218,i.e., is laterally offset from rear cavity 218 away from central axis210. That is, permeable partition 222 may cross back volume 216 along aplane such that a normal vector 250 emerging from first side 224 andpointing into a rear cavity 218 is oriented in a direction orthogonal tocentral axis 210. For example, rear cavity 218 and adsorption cavity 220may each be flat and thin and positioned side-by-side. As a result,sound emitted rearward from diaphragm 206 may propagate directly towarda rear wall of rear cavity 218, rather than be radiated directly towardpermeable partition 222.

In an embodiment, audio speaker 106 includes axially arranged backvolume 216 cavities. For example, adsorption cavity 220 may be locateddirectly behind rear cavity 218. That is, central axis 210 may intersectrear cavity 218 behind diaphragm 206 and adsorption cavity 220 on anopposite side of permeable partition 222. Accordingly, permeablepartition 222 may cross back volume 216 along a plane such that normalvector 250 emerging from first side 224 and pointing into rear cavity218 is oriented in a direction that is parallel to central axis 210. Forexample, rear cavity 218 and adsorption cavity 220 may each be flat andthin and positioned forward-and-behind along central axis. Thus, soundemitted rearward by diaphragm 206 may propagate along central axis 210directly through rear cavity 218 and permeable partition 222 intoadsorption cavity 220.

Permeable partition 222 may be oriented at any angle relative to centralaxis 210. That is, although first face may face a direction orthogonalto, or parallel to, central axis 210, in an embodiment, permeablepartition 222 is oriented at an oblique angle relative to central axis210. Thus, adsorption cavity 220 may be some combination of lateral to,or directly behind, adsorption cavity 220 within the scope of thisdescription. In any case, rear cavity 218 and adsorption cavity 220 maybe adjacent to one another such that opposite sides of permeablepartition 222 define a portion of each cavity.

Referring to FIG. 8, a flowchart of a method of forming an audio speakerhaving a multi-cavity back volume is shown in accordance with anembodiment. At operation 802, housing 204 may be overmolded aroundpermeable partition 222. For example, permeable partition 222 may be athin-walled sheet, plate, or mesh having the structure described above,and may be loaded into an injection mold before molding housing 204around perimeter 304 of permeable partition 222. The overmoldedenclosure may include housing 204 with a multi-cavity back volume 216defined on either side of permeable partition 222. In particular,permeable partition 222 may separate rear cavity 218 on first side 224from adsorption cavity 220 on second side 226, and a seal, e.g., ahermetic seal, may be formed around perimeter 304 due to an overlapbetween housing 204 and partition wall 402. Thus, housing 204 mayinclude rear cavity 218 separate from, and in fluid communication with,adsorption cavity 220 through holes 306 of permeable partition 222.Furthermore, the cavities of back volume 216 may be formed directlybetween the surfaces of housing 204 and permeable partition 222.

At operation 804, speaker driver 202 and/or other audio components maybe mounted in audio speaker 106. For example, diaphragm 206 and/orspeaker surround 208 may be mounted within a speaker port formed inhousing 204. The speaker port may be a circular port that speakersurround 208 is sealed against to support diaphragm 206, for example.The speaker port may be formed during the molding process, e.g., theinjection mold may include geometry that defines speaker port.Alternatively, the speaker port may be formed in a secondary operation,e.g., by drilling or milling a port of the desired size and geometrythrough a wall of housing 204 that encloses rear cavity 218. Thus,speaker driver 202 may partially define rear cavity 218 of back volume216. For example, with speaker surround 208 mounted around the speakerport, a rear surface of diaphragm 206 may define a portion of theenclosure around rear cavity 218.

At operation 806, adsorptive material may be loaded into adsorptioncavity 220. In an embodiment, fill port 228 is formed through housing204. For example, fill port 228 may be formed during the moldingprocess, e.g., the injection mold may include geometry that defines fillport 228. Alternatively, fill port 228 may be formed in a secondaryoperation, e.g., by drilling or milling a port of the desired size andgeometry through a wall of housing 204 that encloses adsorption cavity220. After forming fill port 228, adsorptive filler 232 may be insertedthrough fill port 228 to at least partially fill adsorption cavity 220.For example, adsorptive filler 232 in the form of a powder or othergranular material may be poured into adsorption cavity 220 through fillport 228. As described above, adsorptive filler 232 may partially,substantially, or completely fill adsorption cavity 220. For example,the adsorptive particulate (including interstitial spaces betweenparticles) may have a volume that is at least 95% of the volume ofadsorption cavity 220, and in some cases more than 98% of the volume ofadsorption cavity 220.

In an embodiment, inserting adsorptive filler 232 may involve injectinga combination of adsorptive material and adhesive material such that theadsorptive filler 232 adheres to inner surface 302 of housing 204 aroundadsorption cavity 220. The combination of adhesive and granules may beinjected, for example, through a pressurized delivery nozzle that isinserted through fill port 228 and then directed toward inner surface302 to spray the adsorptive composition against the cavity wall. Thus,inserting adsorptive filler 232 into adsorption cavity 220 may includecoating a portion of inner surface 302 of housing 204 around adsorptioncavity 220 with adsorptive filler 232.

At operation 808, fill port 228 may be sealed to enclose adsorptioncavity 220. For example, plug 230 may be press fit into fill port 228,or alternatively, plug 230 may be flowed and cured within fill port 228to seal fill port 228 against the escape of air and/or adsorptive filler232 from adsorption cavity 220. As a result, plug 230 may partiallydefine adsorption cavity 220, along with inner surface 302 of housing204 and second side 226 of permeable partition 222. Accordingly,adsorption cavity 220 may be fully enclosed to prevent the escape ofadsorptive filler 232.

Referring to FIG. 9, a schematic view of an electronic device having amicro speaker is shown in accordance with an embodiment. As describedabove, electronic device 100 may be one of several types of portable orstationary devices or apparatuses with circuitry suited to specificfunctionality. Thus, the diagrammed circuitry is provided by way ofexample and not limitation. Electronic device 100 may include one ormore processors 902 that execute instructions to carry out the differentfunctions and capabilities described above. Instructions executed by theone or more processors 902 of electronic device 100 may be retrievedfrom local memory 904, and may be in the form of an operating systemprogram having device drivers, as well as one or more applicationprograms that run on top of the operating system, to perform thedifferent functions introduced above, e.g., phone or telephony and/ormusic play back. For example, processor 902 may directly or indirectlyimplement control loops and provide drive signals to voicecoil 212 ofaudio speaker 106 to drive diaphragm 206 motion and generate sound.

Audio speaker 106 having the structure described above may include backvolume 216 separated by an acoustically transparent barrier, e.g.,permeable partition 222, into two cavities: rear cavity 218 directlybehind speaker driver 202 and adsorption cavity 220 adjacent to rearcavity 218 across permeable partition 222. Furthermore, adsorptioncavity 220 may be directly filled with an adsorptive material such thatback volume 216 includes an adsorptive volume defined directly between asystem housing 204 and the acoustically transparent barrier. Theadsorptive volume may reduce the overall spring rate of back volume 216and lower the natural resonance peak of audio speaker 106. That is,adsorptive filler 232 may adsorb and desorb randomly traveling airmolecules as pressure fluctuates within back volume 216 in response to apropagating sound. As a result, audio speaker 106 may have a higherefficiency at lower frequencies, as compared to a speaker having a backvolume 216 without adsorptive material. Thus, the overall output powerof audio speaker 106 may be improved. More particularly, audio speakeroutput, e.g., during telephony or music play back, may be louder,especially within the low frequency audio range. Accordingly, audiospeaker 106 having the structure described above may produce louder,richer sound within the bass range using the same form factor as aspeaker back volume without multiple cavities, or may produce equivalentsound within the bass range within a smaller form factor. Furthermore,since adsorption cavity 220 is defined directly between housing 204 andpermeable partition 222, which are sealed together, the form factor ofaudio speaker 106 may be smaller than, e.g., a speaker back volume thatholds a secondary container, e.g., a mesh bag, filled with an adsorbentmaterial.

In the foregoing specification, the invention has been described withreference to specific exemplary embodiments thereof. It will be evidentthat various modifications may be made thereto without departing fromthe broader spirit and scope of the invention as set forth in thefollowing claims. The specification and drawings are, accordingly, to beregarded in an illustrative sense rather than a restrictive sense.

What is claimed is:
 1. An audio speaker, comprising: a housing defininga back volume behind a speaker driver, wherein the speaker driver is toconvert an electrical audio signal into a sound, the sound to propagatethrough a gas in the back volume; a permeable partition having an outeredge, wherein the outer edge is sealed to the housing to divide the backvolume into a rear cavity defined between the speaker driver, thehousing, and the permeable partition and an adsorption cavity definedbetween the housing and the permeable partition, wherein the permeablepartition includes a plurality of holes that allow sound to propagatedirectly between the rear cavity and the adsorption cavity, and whereinthe plurality of holes have respective hole dimensions; an adsorptivefiller in the adsorption cavity to adsorb the gas, wherein theadsorptive filler includes granules having respective outer dimensionsgreater than the respective hole dimensions such that the permeablepartition constrains the granules within the adsorption cavity, andwherein the granules are movable against the permeable partition and thehousing within the adsorption cavity; a fill port configured to fill theadsorption cavity with the adsorptive filler, the fill port including ahole extending through the housing between the adsorption cavity and asurrounding environment; and a plug in the fill port, wherein the plugincludes a plug shape to form a press fit between a surface of the plugand the housing within the hole of the fill port to create a stopperthat seals the adsorption cavity to prevent the adsorptive filler frompassing through the fill port from the adsorption cavity to thesurrounding environment.
 2. The audio speaker of claim 1 furthercomprising a hermetic seal along the outer edge between the permeablepartition and the housing.
 3. The audio speaker of claim 2, wherein theplurality of holes are configured to prevent the adsorptive filler frompassing between the adsorption cavity and the rear cavity.
 4. The audiospeaker of claim 3, wherein the permeable partition includes a meshhaving a plurality of strands, and wherein the holes are between theplurality of strands.
 5. The audio speaker of claim 3, wherein thespeaker driver includes a diaphragm that moves along a central axis, andwherein the rear cavity is directly behind the diaphragm along thecentral axis.
 6. The audio speaker of claim 5, wherein the adsorptioncavity is laterally offset from the rear cavity away from the centralaxis.
 7. The audio speaker of claim 6, wherein a first side of thepermeable partition faces the rear cavity in a direction orthogonal tothe central axis.
 8. The audio speaker of claim 5, wherein theadsorption cavity is directly behind the rear cavity along the centralaxis.
 9. The audio speaker of claim 8, wherein a first side of thepermeable partition faces the rear cavity in a direction parallel to thecentral axis.
 10. The audio speaker of claim 5, wherein the adsorptivefiller covers a portion of the housing within the adsorption cavity. 11.The audio speaker of claim 10, wherein the adsorptive fillersubstantially fills the adsorption cavity.
 12. The audio speaker ofclaim 11, wherein the granules of the adsorptive filler are looseadsorbent particles.
 13. The audio speaker of claim 12, wherein theloose adsorbent particles include one or more of a zeolite material oran activated carbon material.
 14. A method, comprising: molding ahousing around an outer edge of a permeable partition, wherein moldingthe housing around the outer edge of the permeable partition includessealing the outer edge of the permeable partition to the housing,wherein the housing defines a back volume, wherein the permeablepartition divides the back volume into a rear cavity and an adsorptioncavity and includes a plurality of holes that allow sound to propagatedirectly between the rear cavity and the adsorption cavity, wherein theplurality of holes have respective hole dimensions, and wherein thehousing includes a driver port and a fill port, the fill port includinga hole extending through the housing between the adsorption cavity and asurrounding environment; mounting a speaker driver in the driver portsuch that the rear cavity is defined between the speaker driver, thehousing, and the permeable partition, wherein the speaker driver is toconvert an electrical audio signal into a sound, the sound to propagatethrough the gas in the back volume; inserting an adsorptive filler intothe adsorption cavity through the fill port to fill the adsorptioncavity, wherein the adsorptive filler includes granules havingrespective outer dimensions greater than the respective hole dimensionssuch that the permeable partition constrains the granules within theadsorption cavity, and wherein the granules are movable against thepermeable partition and the housing within the adsorption cavity; andsealing the fill port with a plug such that the adsorption cavity isdefined between the plug, the housing, and the permeable partition,wherein the plug includes a plug shape to form a press fit between asurface of the plug and the housing within the hole of the fill port tocreate a stopper that seals the adsorption cavity.
 15. The method ofclaim 14 further comprising a hermetic seal along the outer edge betweenthe permeable partition and the housing.
 16. The method of claim 15,wherein the plurality of holes are configured to prevent the adsorptivefiller from passing between the adsorption cavity and the rear cavity.17. The method of claim 16, wherein the speaker driver includes adiaphragm that moves along a central axis, and wherein the rear cavityis directly behind the diaphragm along the central axis.
 18. The methodof claim 17, wherein inserting the adsorptive filler into the adsorptioncavity includes coating a portion of the housing within the adsorptioncavity with the adsorptive filler.
 19. The audio speaker of claim 1,wherein the adsorptive filler fills at least 75% of a volume of theadsorption cavity, and wherein the adsorptive filler does not completelyfill the volume.
 20. The audio speaker of claim 1, wherein the housingis overmolded around the outer edge of the permeable partition such thatthe outer edge is in a slot of the housing to seal the outer edge to thehousing.
 21. The method of claim 14, wherein molding the housingincludes overmolding the housing around the outer edge of the permeablepartition such that the outer edge is in a slot of the housing to sealthe outer edge to the housing.